Stabilized photographic emulsions



2,865,749 STABILIZED rnorooaarnrc EMULSIONS James A. Van Allan, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application November 6, 1956 Serial No. 620,572

This invention relates to fog-inhibiting agents and stabilizers for photographic emulsions, and to--photographieemulsions containing them.

It is well known that photographic emulsions'on storage tend to lose sensitivity and to become spontaneously developable without exposure to light. There is normally a detectable amount ofthe silver salt reduced during development inthe areas where no exposure was given; this is commonly called fog, and sometimes called chemical fog where it is necessary todistinguish between it and the effects of accidental exposure to radiation; in this invention, I am not concerned with the latter.

Fog depends both on the emulsion and the conditions of development; for a given emulsion it increases with the degree of development. With constant development conditions, it tends to increase with time, temperature and relative humidity of storage conditions; it is common practice to make accelerated tests of the stability of photographic emulsions by storage at increased temperature or humidity, or both. It is, of course, desirable have emulsions as stable as possible under the conditions of high temperature and humidity which may occur in tropical climates, for example. Fog usually appears over the whole area of the sensitive coating, but when severe, it frequently is non-uniform. Fog may also be caused by expo-sure to chemicals, for example, hydrogen sulfide, and other reactive sulfur compounds, hydrogen peroxide vapor, and strongly reducing materials. While antifoggants and stabilizers may protect, to some extent, against such effects, it is normally understood that an antifoggant protects against spontaneous growth of fog during prolonged storage or storage at high temperatures and humidities, or during development to maximum contrast and speed, or both.

It is, accordingly, an object of my invention to provide a method for'stabilizing photographic emulsions. A further object is to maintain the sensitivity and fog of silver halide emulsionsat or close to initial optimum values under keeping conditions of high temperature and humidity. A further object is to provide photographic silver halide emulsions containing antifoggants or stabilizers. Still another object is to provide new chemical compounds and methods for making suchcompounds. Other objects will become apparent from a consideration of the following description and examples.

According to my invention, photographic silver halide emulsions are stabilized by incorporating therein a compound selected from those represented by the following general formula:

wherein D represents the atoms necessary to comple'te a heterocyclic nucleus of the quinoline series, the benzene ring of which can have substitutedthereQnsubstituentS,

2,65,?49 Patented Dec. 23, 1958 such as methyl, ethyl, chlorine, bromine, hydroxyl, methoxyl, ethoxyl, amino, etc., and Q represents a nitrogen atom or a CR= group wherein R represents a hydrogen atom, an alkyl group (e. g., methyl, ethyl, proply, isopropyl, butyl, etc.) or an'aryl group (e. g., phenyl, hydroxyphenyl, sulfophenyl, naphthyl, hydroxynaphthl, hydroxysulfona'phthyl, hydroxysulfophenyl, etc., especially an a'ryl group containing from 6 to 10 carbon atoms). Also,"'-R can, in certain instances, represent a hydroxyl group. The compounds represented by Formula I above wherein Q represents a methine group (CR=) can be quaternated'with an alkyl ester, such as methyl p-toluenesulfonate, ethylsulfate, methylsulfate, etc., to provide compounds which, in certain instances, have useful stabilizing eflects when incorporated in photographic silver halide emulsions.

The fog inhibitorswhich I propose to use are added to the emulsion during" the process of manufacture, to avoid loss of sensitivity and to inhibit the growth of fog with passage of time under non-ideal conditions of storage.

A solution of the compounds of the invention when added in suitable concentration, before coating, to unsensitized, chemically sensitized, or optically sensitized photographic emulsions does not appreciably aifect the sensitometric values for sensitivity and fog when measurements are made soon after coating. When sensitometric measurements are made at appreciable intervals of time, at elevated temperatures and dry or somewhat humid conditions, these compounds do stabilize photographic speed and maintain fog at a low level.

The preparation of silver halide emulsions involves three separate operations: (1) the emulsification and digestio-n or ripening of thesilver halide, (2) the freeing of the emulsion from excess soluble salts, usually by washing, and (3) the second digestion or after-ripening to obtain increased sensitivity. (Meesl, The Theory of the Photographic Process (1942).) -I prefer to add the fog-inhibiting agents after the final digestion or afterripening, although they can advantageously be added prior to digestion.

Listed below are a number of compounds coming with- 2,3,9b-triazabenz [g] indene 1-methyl-2,3,9b triazabenz ig]ili'dene 1 etliy1 2,3,9b-triazalieria[gl'intlne t- 1-isopropyl-2,3,9b-triazabenz [g] indene 5. HO-C='N O=C-N-H 1-hydroxy-2,3.9b-triazabenz [g] indene C 6HS?=N l- (2-hyd1-oxypheny1 -2,3,9b-triazabenz [g] indene X222. IQ, Cb J 1- (1-hydroxy-2-naphthyl) -2,3,9b-t.riazabenz g] indene GE net's 1- (2-hydroxy-5-sulfopheny1) -2,3,9btriazabenz [glindene noas on 1- l-hydroxy-4-su1fo-2-naphthyl)-2,8,9b-triazabenz [g] Indene 1,8-bis (2.3,9b-triazabenz Ig inden-l-yl) octane 1,2,3,;)b-tetrazabenz [g]indene The compounds of Formula I above wherein Q represents a methine group and R represents a hydrogen atom, an alkyl group or an aryl group have been found to be particularly useful in practicing my invention. Compounds wherein R represents a hydroxyl group are not generally as useful.

The photographic emulsions used in practicing my invention are generally of the developing-out type; also, it is to be understood that photographic emulsions of var ing halide content can advantageously be used. The antifoggant compounds used in my invention have been found particularly useful when employed in conjunction with gelatino-silver bromiodide emulsions, although they can also be advantageously employed for stabilizing other silver halide emulsions, such as gelatino-silver-chloride, bromide, chlorobromide, chlorobromiodide, etc.

The emulsions can also be chemically sensitized by any of the accepted procedures. The emulsions can be digested with naturally active gelatin, or sulfur compounds can be added such as those described in Sheppard U. S. Patent 1,574,944 and U. S. 1,623,499, and Sheppard and Brigham U. S. Patent 2,410,689.

The emulsions can also be treated with salts of the noble metals such as ruthenium, rhodium, palladium, iridium and platinum, all of which belong to group VIII of the periodic table of elements and have an atomic weight greater than 100. Representative compounds are ammonium chloropalladate, potassium chloroplatinate and sodium chloropalladite, which are used for sensitizing in amounts below that which produces any substantial fog inhibition, as described in Smith and Trivelli U. S. Patent 2,448,060, and as antifoggants in higher amounts, as described in Trivelli and Smith U. S. Patents 2,566,245 and 2,566,263.

The emulsion can also be chemically sensitized with gold salts as described in Waller and Dodd U. S. Patent 2,399,083, or stabilized with gold salts as described in Damschroder U. S. Patent 2,597,856 and Yutzy and Leermakers U. S..Patent 2,597,915. Suitable compounds are potassium chloroaurite, potassium aurithiocyanate, potassium chloroaurate, auric trichloride and 2-aurosulfobenzothiazole methochloride.

The emulsions can also be chemically sensitized with reducing a ents such as stannous salts (Carroll U. S. Patent 2,487,850), polyamines such as diethylene triamine (Lowe and Jones U. S. Patent 2,518,698), polyamines, such as spermine (Lowe and Allen U. S. Patent .2,52l.925), or bis-(,B-aminoethyUsulfide and its watersolublesalts (Lowe and Jones U. S. Patent 2,521,926).

The emulsions can alsobe stabilized with the mercury compounds of Allen, Byers and Murray U. S. Patent 2,728,663, Carroll and Murray U. S.'Patent 2,728,664, and Leubner and Murray U. S. Patent 2,728,665.

The stabilizing combinations of my compounds are effective in the presence or absence of ootical sensitizing dyes. Since optical sensitizing may affect stability of emulsionswith respect tosensitivity, fog and latent image changes, the action of the compounds of this inventionis not completely independent of optical sensitizing or other emulsion variables. I havefound, however, that both un-sensitized emulsions and emulsions sensitized with cyanine or merocyanine dyes, or both, can be treated with triazabenzindenes according to my invention.

The antifoggant and/or stabilizing action was determined by incubation of the emulsions for one or two weeks at a temperature of 120 F. and constant relative humidity (obtained by placing the emulsions in closed containers, the ambient temperature being about 70 F. and relative humidity about 50-55 percent prior to scaling the containers).

The etficiency of the various antifoggants was determined by measuring the speed, gamma and" fog of the incubated emulsions containing an antifoggant and comparing these measurements wi.h those of the same batch of emulsion before incubation. Also, similar measurements were made wiLh a photographic emulsion containing no antifoggant both before and after incubation.

The tests were made using high speed, negative-type silver bromiodide emulsions (coated on cellulose acetate supports), which had been panchromatically sensitized with a cyanine dye and chemically sensitized with sulfur and gold compounds. The test fi'ms were exposed on an intensity scale sensitometer and developed for 5 minutes in a developer having the following composition:

Grams N-methyl-p-aminophenol sulfate 2.5 Hydrcquinone 2.5 Sodium suifite 30.0 Sodium metaborate 10.0 Potassium bromide 0.5

Water to make 1 liter.

The speed, gamma and fog for each of the emulsion coatings were then measured as indicated above. The speed figures given in the following table are on a logarithmic scale obtained by the formula: 100(1-log E), where E is the exposure in meter candle seconds of sunlight quantity radiation required to produce a. density of 0.30 above fog. However, the speed figures in Examples 12 and 13 of the following table are on the basis of 30/E, which is a conventional means of measuring speed. This change in speed measurement has been designated by a double asterisk. The single asterisk of Example 5 means that the incubation period in this one instance was for two weeks rather than one week, as was the case for the other examples. The results obtained follow:

TABLE I Com- Fresh Tests Incubation Example pound (g /rr ole AgX) Speed Gamma Fog Speed G amma Fog 306 1. 31 .15 280 1.07 23 307 1. 40 .13 295 1.24 15 305 1.11 .10 297 .95 .18 305 .98 .11 301 .91- .11 305 l. 13 14 295 87 29 296 1.01 14 290 .91 .17 305 1.13 .14 295 .87 .29 279 1. 26 262 1.07 17 316 1.25 .13 259 .85 .48 293 83 11 287 .86 16 309 1. 32 18 290 1.05 .24 307 1. 37 .16 295 1.05 .21 309 1.32 18 290 1.05 .24 308 1. 63 290 1. 30 305 1.27 .15 295 1. 06 .25 302 .82 .14 301 .7 .20 317 1.44 .15 310 1.06 .19 314 1. 50 .12 304 1.00 .12 309 1. 32 18 290 1. 05 .24 307 1.35 .15 293 LC!) .17 305 1.13 .14 295 .87 .29 266 1. 04 .08 253 .97 08 5,100 1.10 .12 4, 450 1.04 .18 2, 600 1.16 .10 2, 550 1.25 .11 5, 450 .96 16 3, 450 .88 .25 5, 100 1. 20 14 3, 700 1.03 19 In a manner similar to that illustrated in the above examples, other compounds selected from those represented by the above general Formula I can be incorporated in photographic emulsions for the purpose of stabilization. The fog-inhibiting agents useful in prac' ticing my invention can be used in various kinds of photographic emulsions. In addition to being useful in ordinary non-sensitized emulsions, they can also be used in ortho-chromatic, panchromatic and X-ray emulsions. If used with sensitizing dyes, they can be added to the emulsion before or after the dyes are added. Suitable dispersing agents for the silver halide emulsions stabilized according to my invention comprise gelatin, or other colloids, such as collodion, albumen, cellulose organic derivatives, synthetic resins, etc.

The optimum amount of fog-inhibiting agent can .be determined by making the customary tests employed in emulsion making. Of course, the optimum amount for a given emulsion will vary depending on the presence of emulsion addenda, such as chemical sensitizers, optical sensitizers, etc. In general, I have found that from 0.001 to 5.0 g. of fog-inhibiting agent per mole of silver halide is sufficient for the purposes of my invention.

Instead of adding the fog-inhibiting agent directly to the photographic emulsion, it is sometimes desirable to incorporate the fog-inhibiting agent in a separate layer which is placed in contact with the silver halide emulsion layer which is to be stabilized. Under such conditions, it is advisable to use a higher concentration of fog-inhibiting agent than indicated above. The antifogg nts of my invention function advantageously in acid or alkaline photographic silver halide emulsions.

The compounds selected from those represented by Formula I above wherein Q represents a -CR= group and R represents a hydrogen atom or a lower alkyl group can advantageously be prepared by condensing a compound selec ed from those represented by the following general formula:

II. N

formula: n1. R1 2)3 wherein R represents a hydrogen atom or a lower alkyl group, such as methyl, ethyl, etc. and R represents a lower alkyl group, such as methyl, ethyl, etc. This method can be summarized as follows:

Procedure A.-A mixture of 0.1 mol. of the heterocy-clic hydrazine (Formula II) and 0.11 mol. of the orthoester (Formula 111) in 60 ml. of xylene was refluxed for 3 to 4 hours in a flask surmounted with an efficient fractionating column. The alcohol which was form-ed was continuously removed. When the theoretical amount of alcohol (0.3 mol.) had been collected, the reaction was considered to be complete.

The compounds of Formula I wherein R represents a higher alkyl group or an alkyl group containing a substituent, such as chlorine, carboxyl, etc., can advantageously be prepared by condensing the compound selected from those represented by Formula II above with an acid selected from those represented by the following general formula:

wherein R represents a higher alkyl group, such as butyl, amyl, etc., or a substituted alkyl group, such as fi-carboxyethyl, -hydroxypropyl, etc. The dicarboxylic acids embraced by Formula IV should generally have at least two carbon atoms between the carboxyl groups.

The compounds of Formula 1 wherein R represents a hydroxyaryl group can advantageously be prepared by condensing a compound selected from those represented by Formula 11 above with a compound selected from those represented by the following general formula:

ma-coon:

wherein R has the values given above and D represents the atoms necessary to complete a benzene ring (which can have substitutents thereon, such as methyl, ethyl, hydroxyl, etc.). This method of preparation can be summarized as follows:

Procedure B.A mixture of 0.1 molar quantities of the o-hydroxy-phenyl ester (Formula V) and of the beterocyclic hydrazines in 50 ml. of 1,2,4-trichlorobenzene was refluxed. The water which was formed distilled over first at 98-101 C. The temperature at the stillhead then rose and phenol distilled over at ISO-190 C. The reaction was considered complete when the stillhead temperature was 203 C. Reaction was usually complete in about 2 hours.

The compounds of Formula I wherein R represents a hydroxyl group can be prepared by condensing a compound selected from those represented by Formula II above with a compound selected from those represented by the following general formula:

VI R4NCO wherein R represents an aryl group, such as phenol, tolyl, etc. This method can be summarized as follows:

Procedure C.A mixture of 0.1 mole of the isocyanate (Formula VI) and heterocyclic hydrazine in 60 ml. of trichlorobenzene was refluxed for about 2.5 hours. 7 After cooling to room temperature the crystals which had separated were collected by filtration and washed well with benzene and extracted twice with 400 ml. portions of warm percent sodium hydroxide.

The extracts were combined and acidified with acetic acid. The precipitate was collected by filtration and crystallized from a suitable solvent.

The condensation of the compounds of Formula II with those of Formula IV above can be summarized as follows:

Procedure D.The procedure for cyclization with phenol was as follows: The heterocyclic hydrazine and a large excess of the appropriate aliphatic acid (Formula IV) were refluxed two hours, cooled, and the acyl hydrazine collected by filtration. The acyl hydrazine was refluxed 2-20 hours with 2.5 times its weight of phenol and the phenol then removed by steam distillation. The residue was either recrystallized or first distilled in vacuo and then recrystallized.

The compounds of Formula I above wherein Q represents a nitrogen atom were prepared by condensing the heterocyclic hydrazine of Formula II above with nitrous acid. This method can be summarized as follows:

Procedure E.-Nitrous acid ring closure: The heterocyclic hydrazine was dissolved in 15 times its weight of 50 percent aqueous acetic acid, the solution cooled, and added the calculated amount of sodium nitrite in a small amount of water. The tetraza compound usually separated at once, but the reaction mixture was allowed to 1 stand in the cold for an hour before collecting the product.

The compounds of Formula I above wherein R represents an aryl group can also be prepared by condensing a compound selected from those represented by the following general formula:

VII. 1N

wherein D has the values given above with a compound selected from those represented by the following general formula:

wherein R; has the values given above. This method can be summarized as follows:

Procedure F.A mixture of 0.1 mole each of the compound of Formula VI, the compound of Formula VIII, and sodium phenoxide in 40-50 ml. of phenol was refluxed for 20 hours. The solvent was steam distilled and the residue recrystallized from an appropriate solvent. In cases where sodium phenoxide is omitted, slightly lower yields of product were obtained.

The following examples will serve to illustrate the methods for preparing certain of the compounds of Formula I.

Example A.2,3,9b-triazabenz[g]indene N 111112 Ilq @J-NH ncrooiuat @JN -r Ten grams of 2-hydrazinoquinoline and 50 ml. of ethyl orthoformate were refluxed using a Fensky column and continuously removing the alcohol as it was formed. After ll ml. of alcohol had been collected (about 2 hours), the mixture was cooled and the product filtered off and crystallized from isobutanol to give 4 g. of product, M. P. 175 C. Analysis for C H N Calcd: C=71.5; H=3.6. Found: C=71.3, l-l=4.0.

Example B.-1,2,3,3a-tetrazabenz0[e]indene A solution of 25 g. (0.157 mole) of 2-hydrazinoquinoline in 500 ml. of 50 percent aqueous acetic acid was cooled below 10 C. and a concentrated aqueous solution containing 10 g. of sodium nitrite was added slowly with stirring. The mixture was allowed to stand in the refrigerator overnight and the solid collected and recrystallized from a large volume of water to give 10 g. of product melting at 157 C.

The compounds of Formula I above wherein Q represents a nitrogen atom can also be prepared by condensing a compound selected from those represented by Formula VII above with sodium azide. This method can be illustrated as follows:

A mixture of 16.4 g. of 2-chloroquinoline and 8.0 g. of sodium azide in 60 ml. of 15 percent aqueous ethanol was refluxed for 6 hours. The solution was filtered while still hot. On chilling, 8.0 g. of the desired product (l,2,3,9a-tetrazabenz[e]indene. M. P. 153-4 C.) separated. A mixed melting point with an authentic sample of the desired compound showed no depression of melting point.

The intermediates selected from those represented by Formula II have previously been described in the prior art. See, for example, Berichte, vol. 33, pages 1885-99.

The alkyl salts of the compound of Formula I wherein Q represents a -CR group can be prepared according to known methods of quaternization, such as by simply heating the compound of Formula I above wherein Q represents a -CR': group with an alkyl salt in an oil bath. Such a general method of preparation is shown in Brooker U. S. Patent 2,743,274, issued April 24, 1956.

The condensation of the compounds of Formula II with the dicarboxylic acids represented by Formula IV above (i. e., wherein R is a carboxyalkyl group) is quite similar to condensations described in my copending application Serial No. 620,598. filed on even date herewith. Typical carboxylic acids embraced by Formula IV above include succinic acid, tartaric acid, adipic acid, pimelic acid, sebacic acid, etc. This condensation is also similar to the .condensations described in Tinker U. S. application Serial No. 612.598, filed September 28, 1956 (now U. S. Patent 2,852,375, issued September 16, 1958).

The tollowing table summarizes the physical data for a number of compounds obtained according to the general TABLE II Analysis Analysis M. P., Yield, alcd. Found Compound O. Method Solvent Percent H O H 175 A isobutanol 40 71. 3. 6 71. 3 4. 0 176 A do 78 72.0 4.9 72. 4 5. 2 123 A toluene 84 73. 1 5. 6 73. 5 5. 7 83-4 D ligroin 58 72. 4 6. 5 72. 5 6. 4 248 C butanol 65 65.0 3. 8 65.0 3.7 89 F benzene-ligroin 76 79. 0 4. 5 79. l 5. 0 290 B dimethyl-sulione.. 87 73. 5 4. 2 73. 5 4. 5 289 B triohloro-benzene 77 77. 1 4. 2 77.3 4. 0

What I claim as my invention and desire secured by Letters Patent of the United States is:

1. A photographic silver halide emulsion containing a compound selected from those represented by the following general formula:

wherein D represents the nonmetallic atoms necessary to form a quino-line ring and Q represents a member selected from the group consisting of a nitrogen atom and a CR group wherein R represents a member selected from the group consisting of a hydrogen atom, an alkyl group containing from 1 to 4 carbon atoms and an aryl group.

2. A photographic gelatino-silver-halide developing-out emulsion containing a compound selected from these represented by the following general formula:

wherein D represents the nonmetallic atoms necessary to form a quinoline ring and R represents a member selected from the group consisting of a hydrogen atom, an alkyl group containing from 1 to 4 carbon atoms and an aryl group containing from 6 to 10 carbon atoms.

3. A photographic gelatino-silver-halide developing-out emulsion according to claim 2 wherein the silver halide is silver bromiodide.

4. A photographic gelatino-silver-halide developing-out emulsion containing a compound selected from those represented by the following general formula:

wherein R repersents a member selected from the group consisting of a hydrogen atom, an alkyl group containing from 1 t0 4 carbon atoms and an aryl group containing from 6 to 10 carbon atoms and R represents a member selected from the group consisting of a hydrogen atom and an alkyl group containing from 1 to 2 carbon atoms.

5. A photographic gelatino-silver-halide developing-out emulsion according to claim 4 wherein the silver halide is silver bromiodide. Y

6. A photographic gelatino-silver-halide developing-out emulsion containing a compound selected from those represented by the following general formula:

N N o wherein D represents the ponmetallic atoms necessary to form a quinoline ring.

7. -A photographic gelatino-silver-halide developing-out emulsion containing a compound selected from those represented by the following general formula:

10. A photographic silver halide emulsion containing the compound represented by the following formula:

11. A photographic silver halide emulsion containing the compound represented by the following formula:

N HO3|S i):

12. A photographic silver halide emulsion containing the compound represented by the following formula:

13. A photographic silver halide emulsion containing the compound represented by the following formula:

ll 14. A photographic element comprising a silver halide emulsion layer and a colloid layer, at least one of said layers having incorporated therein a compound selected from those represented by the following general formula:

form a quinoline ring and Q represents a member se- 12 lected from the group-consisting of a nitrogen atom and a CR group wherein R represents a member selected from the group consisting of a hydrogen atom, an alkyl group containing from 1 to 4 carbon atoms and an aryl 5 group.

References Cited in the file of this patent FOREIGN PATENTS 667,206 Great Britain Feb. 27, 1952 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION ?atent No 2365 7749 December 23, 1958 James A Van Allan It is herebfir certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1,, line 35, after "desirable" insert to column 2 line 5 for "proply" read propyl line '7, for "naqmtlrl read m1 naphthyl line 36, for "Mee-sl" read Mees. column 9, line 56, for "repersents" read represents Signed and sealed this 5m day of May 1959,.

(SEAL) Attest:

KARL H, AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents 

1. A PHOTOGRAPHIC SILVER HALIDE EMULSION CONTAINING A COMPOUND SELECTED FROM THOSE REPRESENTED BY THE FOLLOWING GENERAL FORMULA: 